Airport heating and airport fog dispersal



Oct. 9, 1951 P. L. GEIRINGER 2,570,226

AIRPORT HEATING AND AIRPORT FOG DISPERSL Filed oct. so, 1947 4 sheets-Sheet 1 Oct. 9, 1951 P. l.. GEIRINGER 2,570,226

AIRPORT HEATING AND AIRPORT Foc; DIsPERsAL Filed Oct. Z50, 1947 4 Sheets-Sheet 2 FZ' 5 IN1/EN TOR:

g PAUL L. GHR/N60?,

..JQ M,

H/S AGEA/I Oct. 9, 1951 P. l.. GEIRINGER 2,570,226

' AIRPORT HEATING AND AIRPORT Foc DIsPERsAL Filed oct. so, 1947 4 sheets-sheet s OUT DN OUT IN1/EN TOR PAUL L. GHR/Nef@ H/S AGENT.

P. L. GEIRINGER 4 Sheets-Sheet 4 AIRPORT HEATING AND AIRPORT FOG DISPERSAL Oct. 9, 1951 Filed Oct. 50. 1947 Ummm Mmm RETURN MA\N FEED P\PE PxPE MNN FEED P\PE 57 v BUF-T5 MAH RETURN PUDE JL ;l.l

,QUI l l l l l DucTS H/S AGE/VT.

Patentd Oct. 9, 1951 UNITED STATES PATENT OFFICE AIRPORT HEATING AND AIRPORT FOG DISIERSAL s claims. 1

The invention relates to the design and malntenance of airport runways and relates more particularly to removal of ice and snow from the runway surface and the dispersal of fog over the runway.

In the past, snow and ice removal on one hand and fog dispersal on the other, were looked upon as distinctly different problems, and the solutions that were advanced attempted to deal with these problems separately.

It is one of the principal objects of the invention to carry out snow removal and fog dispersal using energy for either that is drawn from a unitary source.

Another object of the invention is to provide heat for these purposes at low cost and to con. vey the heat without great heat dissipation to the airport runway.

Another object of the invention is the provision for distributing heat along the runway surface so that more heat will be imparted at certain points of the surface than at others.

Another object of the invention is to provide for quick, eflicient and automatic snow removal and fog dispersal that may be regulated in accordance with the amount of heat energy necessary to deal with instantly prevailing fog and snow conditions.

A further object of the invention is to provide for such snow removal and fog dispersal at a comparatively small cost of maintenance and repair.

A still further object of the invention is the provision of a liquid heat carrier for transporting and discharging high-temperature heat.

Further objects and advantages of the invention will be set forth in part in the following specification and in part will be obvious therefrom without being specifically referred to, the same being realized and attained as pointed out in the claims hereof.

With the above and other objects of the invention in view, the invention consists in the novel methods, construction, arrangement and combination of various devices. elements and parts, as set forth in the claims hereof, certain embodiments of the same being illustrated in the accompanying drawings and described in the specification.

The speedy removal of snow and ice from the runway surface of an airport as well as the rapid dispersal of fog over runways has been sought for by those responsible for airport maintenance, ever since modern landing strips have come into existence.

Airport runways are usually rendered useless by the accumulation of snow or ice, and before further flights can be resumed, the runway must be cleared substantially of all snow and ice.

Likewise, where fog covers an *1port, the use 'of the runways is greatly diminished and often entirely impossible. Although modern instrument flying permits take-off and landing in fog, most pilots still prefer good visibility to the best instruments, particularly for landing. Many attempts have therefore been made to drive fog off the airport site as soon as it appears there, and these attempts have usually followed the line of either directing flames against the fog or, more recently, dropping pellets of Dry Ice into fog for dispersing the same. The former method has not been favored very much since it was recognized to be hazardous for an airplane to land on a strip bordered by flames. The latter method requires the distribution, by spraying, of Dry Ice into the cloud of fog, and that certain favorable atmospheric conditions must prevail before Dry Ice fog dispersal can be carried out successfully; at the present state of development, at least, this manner of fog dispersal does not appear to be invariably applicable under any and all conditions.

The latter method, however, may be favorably used, where the conditions permit, together with the snow removal features of the instant invention; the Dry-Ice defogging will at certain seasons cause, the fog to be converted to snow that will drop onto the airport surface and that snow will have to be removed therefrom, which latter can be carried out as described hereinbelow.

The present invention has for a primary aim to remove snow and ice from runway surfaces and at the same time to disperse fog under substantially any prevailing conditions, to render the runway usable at -all times. The instant invention utilizes the same means for snow removal as well as fog dispersal.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatic plan view of an airport site showing a runway, in connection with which the present invention is utilized;

Fig. 2 is a fragmentary perspective View, partly in vertical transverse section, of an airport runway disclosing certain features of the present invention;

Fig. 3 is a fragmentary vertical sectional view 3 of an airport runway. in accordance with the present invention;

Fig. 4 is a schematic fragmentary plan view of an airport runway showing one embodiment of the invention; v

Fig. 5 is a fragmentary sectional view takenalong line 5-5 of Fig. 4;

Fig. 6 is a schematic fragmentary plan view similar to Fig. 4, but embodying a modification;

Fig. 7 is a fragmentary sectional view taken along line l-l of Fig. 6; and

Fig. 8 is a fragmentary sectional view taken along line 8--8 of Fig. 7. g

In carrying theinvention into effect in the embodiments which have been selected for illustration in the accompanying drawings and for description in this specification, and referring now particularly to Fig. l, a central heat generator or heating plant, generally indicated at I I, is shown where sufficient heat may be created t0 cover the heat requirements for clearing the airport runway of ice and snow and for dispersing fog' surrounding the runway.

The requirements for the purpose involved call for a comparably large heat output, as will be explained in detail later on, and also call for transporting the generated heat over large distances with minimum heat losses during such Itransportation. For this purpose the instant invention utilizes liquid. substantially incompressible fluid, such as water that is heated to high temperatures, preferably considerably above the atmospheric boiling temperature thereof.

ln order to impart high temperature to incompressible fluids, it is necessary to employ high pressure while heating the same and to maintain considerable pressure throughout the circuit of the high-temperature fluid to prevent evaporation at the boiling temperature and to maintain the liquid status of the fluid above the boiling temperature.

The utilization of high-temperature incompressible fluids requires the use of pipes to conduct the fluid throughout its transport circuit, so that adequate pressure may be maintained. .Although'this maintenance of pressure throughout the circuit necessitates the installation and utilization of auxiliary equipment, such as pumps, etc., the employment of high temperature incompressible fluids offers substantial overall advantages for the instant purposes, as compared with other heat transfer means.

A brief survey of other commonly used heat transfer means may serve to emphasize the advantages of utilizing high-temperature water for the instant purpose. One of the well known heat transfer means is steam, and although steam may easily be heated and transported over large distances, its use in large circuits always presents special problems of design and maintenance. Steam has large volume as compared with water and thus requires large diameter piping. Aside from the high cost of the piping and the necessary excavation for it where the piping is laid in a subterranean path, the insulation of steam pipes is quite costly. Furthermore, traps have to be provided at certain intervals for elimination of condensate, and these traps have to be accessible from the outside. Sharp corners and turns have to be avoided to prevent excessive formation of condensate.` Moreover, the excavations for steam pipes require a certain so-called fall, which means that they usually become deeper with increased distance from the steam generating point,

. to provide for condensate collection. Still fursoV thermore, the so-called water hammer by the condensate is an ever present danger for the continued long range operation of steam pipes.

In contrast thereto. high-temperaturefwater or other high-temperature incompressible fluids may be transported in comparably small diameter pipes. It has been found that the viscosity of high-temperature water diminishes with increased temperature and thus relatively small diameter pipes may be utilized. These pipes may be procured at a small cost compared to that of steam pipes, and the insulation wherever required will require less cost than equivalent steam piping. Furthermore, such water pipe lines can be deposited without any fall, can be laid following the contour of the ground and may have as many turns and even sharp corners as might be desired. Noheat exchanges nor secondary circulation pumps have to be installed along the circuit, and condensation traps as well as pressure reducing valves are unnecessary. Still further, no water purification equipment is required, such as is always needed for steam, because no water will be lost, since the hot Water circulates in a closed, airtight circuit and the same water is returned to the generating point for reheating and reuse. The reheating of the returned water permits utilization of any heat that has remained therein, and the returned water has to be heated only for the temperature difference between the returned water and that sent out into the circuit. Moreover, no water hammer danger exists for these high-temperature fluid pipes.

Another well known heat transfer medium is high temperature gas, for instance, hot air. The large specific volume of heated air would require the use of large diameter ducts or pipes, which, in turn, would require expensive equipment and costly excavation and insulation. It has been found that utilization of hot air is entirely uneconomical for transportation over large distances. Yet, for the instant purpose, heat transportation is required over great distances when considering that the length of large airport runways equals about six thousand ft. up to fifteen thousand ft.

High-temperature water can be transportedl economically and Without appreciable heat losses for many miles.

A high-temperature Water circuit may be operated without automatic controls along the circuit, since all of the automatic controls may be operated from a central point, for instance, from the power plant. This feature together with the fact that even great distances between the power plant and the place where heat is tobe applied may be covered Without materially reducing the overall economy of the system, permit the placing of the central heating plant at any desired location, even at a place at some distance from the airport site. The power plant Il may therefore be located at any desired place and will preferably be located in or near the airport administration buildings, and this has been assumed in the exempliiication shown in l. The installation of a high-temperature fluid heating system for the airport runway, permits to extend the fluid-circuit for heating the airport buildings and hangars, which provides for great economy in the construction and maintenance of the entire airport facilities.

The heating plant Il comprises a boiler plant that is equipped with one or more boilers of high capacity for a correspondingly large heat energy output for heating the required amount oi' water continuously to a temperature of 300- 400 F., or higher, for the instant purposes. The heated water may either be pumped directly through transport pipes I 2 to the airport runway I4, or preferably, may first be stored in a hot water storage vessel I5 that may form part of the power plant.

The utilization of a storage vessel or accumulator renders possible the employment of a comparably. small boiler plant since the peak loads may be drawn from the storage vessel; the desired amounts of heat are then drawn from the storage vessel, according to the momentary need that depends to a large extent on the conditions of snow or fog along the runway.` Suitable conventional flow control valves are provided (not shown) to permit withdrawal of heated fluid from the storage vessel at a selectively variable rate. Such an arrangement permits utilization of large amounts of stored hot water for a predetermined period of time, depending on the capacity of the accumulator. The transport pipe I2, in this preferred embodiment, connects the storage vessel and the boilers with the runway I4, and a pipe I3 is provided near the pipe I2 to return the fluid to the boiler plant after it has passed through the heating circuit required for heating the runway surface and dispersing fog thereon. Single or double stage centrifugal pumps are provided to keep the water under a constant heat and to drive it through the circuit.

Conventional temperature measuring instruments are installed at various points of the surface of the runway I4, and these are electrically connected to a central station, such as a control board, in the plant II. Either manually or auto` depends on the amount of snow-fall and the type of atmospheric conditions at such time. If it is very cold the weight of the snow is only 5 to 6 lbs. per cubic ft.; but if the temperature rises to be near 32 F., the weight of the snow can increase up to 14 lbs. per cubic ft.

The average dimensions of a runway are 150x6,000 ft., so that, together with aprons near the runway, an area of about 1,000,000 square ft. for one runway has to be heated.

The runway I 4 is conventionally provided with a surface I6 that is inclined at a small angle (for instance 11/2) at both sides from the longitudinal center, symmetrically, as best shown in Fig. 3, where the inclination, however, has been exaggerated for the purpose of illustration. The runway is bordered on each longitudinal side by a trough I1 to receive water drained from the inclined runway surface I6. Between each longitudinal side of the runway I4 and the trough l1 the instant invention provides for a longitudinal chamber IB that extends substantially throughout the length of the runway and houses the hot water main pipes, namely the main feedpipe I2 and the main return pipe I3. These main pipes I2 and I3 are preferably suspended on rollers I9 to permit longitudinal movement of the pipes due to expansion caused by temperature variations. Since both sides oi' the runway are symmetrically alike, only one side is shown. it being understood that the main feeder pipe I2 and the main return pipe I3 extend on both sides of the runway. The hot water circuit is an endless one, starting at the power plant II. and continuing by means of the main feeder pipe I2, then by the heat discharge equipment that is explained further below, the return main pipe I3, and finally by return of the water to the power plant II.

Above these main pipes I2 and I3 there are provided in the chamber i8 secondary hot water pipes of common headers 22 and 23 that are suspended on rollers 2l which are in turn supported by brackets or other suitable means. Said secondary pipes feeder 22 and return pipes 23 do not extend throughout the length of the runway, but each pipe 22 and 23 extends lengthwise for a small portion of the runway, and consequently a plurality of pipes 22 are provided in alignment in the chamber I8, but independent of one another, and similarly a plurality of axially aligned. though independent, pipes 23. Each secondary feederpipe 22 is connected to the hot water feeding main pipe I2 to receive hot water therefrom, and each secondary return pipe 23 is connected to the main discharge pipe I3 to deliver water thereto that has been used for heating purpose and is being returned to the power plant for reheating.

From the pipes 22 the hot water is conducted into the runway carpet 24, at a point spaced belowthe surface I6, by means of embedded pipe coils or labyrinths 26 to heat the carpet 24 and thereby the surface I6 of the runway. Each labyrinth 25 'comprises several interconnected parallel branch pipes 21 of small diameter, that are embedded in the runway carpet 24 substantially in the form of a cipher 3. Each branch pipe 21 extends to about the longitudinal center line of the runway and formsan acute angle therewith of about 30 to 60, thereby forming `an acute angle with the slope line of the runway.

as shown in the exemplification in the drawing.

Each coil or labyrinth 216 consists of four parallel branch pipes 21, and the labyrinths are arranged below the entire runway surface, symmetrically, with respect to the longitudinal center line of the runway, as best shown in Fig. 4. The hot water is conducted from the secondary pipe 22 to a branch pipe 21 of the labyrinth 26 and flows first towards the center of the runway, then flows in an opposite direction in the second branch pipe 21, thence again towards the center line of the runway, and in the fourth pipe again away therefrom, and finally into the secondary return pipe 23 from where it is discharged into the main pipe I3 for return to the power plant As best shown in Fig. 5, each pipe 21 is embedded in the lower portion of the runway carpet 24. A strip of insulating material 28, for instance made of aluminum foil or asbestos sheet. is provided on top of each branch pipe 21 to provide for an even spreading of the heat radiating from the pipe 21 and to avoid extreme heating of the runway surface area immediately above the pipe 21. The zones of heat radiation are indicated in broken lines in Fig. 5 to illustrate by exemplication the equalized spreading of heat. The width and thickness of the in- '15 sulation 28 varies depending on the temperature drop along the path of the labyrinth 26 that is followed by the interconnected branch pipes 21. vAs shown in Fig. 5, the width and thickness of the insulation 28 on the right hand pipe 'i f the same labyrinth. In this manner the, surface I6 of the runway may be heated substantially equally throughout.

This application of the insulation 28 permits the use of very high temperatures for the water within the pipes and thereby admits of placing the pipes 21 at comparably great distance from one another. This in turn reduces the amount of piping that is embedded in the concrete compared with that which would be necessary if a heat transfer medium of lower temperatures would be used. 'I'he application of the insulation 28 also permits to deposit the pipe at comparably small depths below the surface I6 thereby further reducing the costs of excavation when the pipes are installed. Insteadof providing a separate insulation 28 atop the branch pipes 21. however, the concrete of the runway carpet 24 may itself be provided with insulating properties, for instance by the admixture of foam concrete or mica concrete or diatomaceous earth, to accomplish an equalized spread of heat to the surface I6.

In addition to this upper insulation, an insulating layer 29 composed of a mixture of mica concrete or diatomaceous earth is provided below the entire area of the carpet 24 and thereby below the branch pipes 21, to prevent penetration of the heat into the ground and to direct, instead, the heat onto the surface I6 of the runway.

As has been pointed out in the foregoing, the runway heating pipes 2,1 are disposed at an acute angle to the longitudinal direction of the runway. Since large heat drops are applied, the (first) pipe 21 that receives the hot water directly from the secondary pipe 22 will have a considerable higher temperature than the (last) pipe 21 of the same labyrinth 26 that discharges the water into the pipe 23 after the water has given olf the major part of its heat. As related in the foregoing, the difference in heat among the pipes 21 of the same coil 26 Will be equalized to a great extent in its effect upon heat transmittal tothe surface I6, by the variation in width of the insulation 28. However, `the first branch 21 will start the melting of the snow I that has accumulated on the surface I6, and the angular disposition of this pipe 21 will cause the melted snow to ow, following the slope of the runway, across the unmelted snow and will aid in melting the same. In this manner, the heat of the water in the coils `will be applied with different intensity at different areas oi the runway, and thereby economically towards melting of the snow on the entire surface of the runway.

As shown in Fig. 4, four branch pipes form a coil or labyrinth 26. A plurality of coils 26 are fed by a single secondary pipe 22 and discharge into one single secondary pipe 23. Thus, each of the secondary pipes 22 and 23 serve a section of runway length along one longitudinal side thereof. The adjoining section of runway is serviced by another pair of secondary pipes 22 and 23, and all the secondary pipes communicate by means of suitable piping equipment with the main pipes I2 and Il, and the flow of water thereto may be controlled by valves.

Since the main pipes I2 and I2, as well as the secondary pipes 22 and 23. along one side of the runway, are disposed in the chamoer lo, the heat emanating from these pipes-though all the pipes are conventionally insulated-will be transmitted to the adjacent trough I1. thereby aiding to keep the troughs free from ice and now particles that may have been carried thereinto by the melting snow.

In order to obtain a good heat distribution along the runway surface and to maintain the same free of cracks. itis advantageous to use reinforced, prestressed concrete for the runway carpet 24. To take care of the expansion between the concrete and the pipes when the latter are `installed in embedded position in the concrete. it is advantageous to heat the pipes during the drying of the concrete and to cool them subsequently so that the pipes will thereafter have a slight play and can expand independently of the concrete. It may also be advisable to use a non-insulating wrapping material not shown) around pari of the pipe in order to permit the pipe to detach itself from the surrounding concrete; at the bends of the pipes a free space for expansion will be left. In this way the heat transfer capacity of the pipes willbe slightly impaired due to the air space betwen the pipe surface and the surrounding concrete, but the importance of avoiding excessive stresses in the concrete and in the pipes due to expansion or loading compensates for this slight loss. Instead of embedding the pipes directly into the runway carpet 24, it alternately is possible to install the pipes in a separate layer 29 of concrete below the carpet in accordance with a modification of the invention; cracks that may appear in this layer 29 due to the heat effect in the pipes will not be transmitted to the runway carpet 24 and the latter l will be free of cracks, since this layer and the carpet will move in relation to one another.

The hot water may not only be used to melt snow -as related in the foregoing, but may also be utilized, in addition, to heat air that may be blown above the runway surface to disperse fog.

As shown in Figs. 2 and 3, some of the hot water may be branched olf the main pipes I2 and I3 to be diverted to flow through the coils of several conventional combination heaters-andblowers 3l. Outside air may be drawn through openings 32 of the carpet 24 and be blown through the coils of the heater 3| and then forced through spaced parallel underground ducts orpaths 33 that are disposed substantially transversely below the runway surface, to be finally blown above ground at high velocity, through spaced air exhaust shafts 34. These exhaust shafts may be separated for distances of from 30 to 50 ft, and revolving units (not shown)` may be set up at the intersection of the shafts 34 with the surface I6 to distribute evenly the jet streams or gushes of hot air emanating from the shafts. A blower and heater 3| is provided for each parallel path l33,' alternately at one side of the runway, so that in alternating ducts the air is blown in from different directions.

The temperature of the air stream is brought to a temperature of from -150 F. by the heaters 3I, and the air jets emanating from the shafts 34 on the runway surface will have a temperature of about 100 F. which latter temperature is sufficient to disperse fog successfully.

When revolving units are used to direct the air in a revolving jet, the paths 33 and the air shafts 34 may be spaced for greater distances up to 100 ft. apart.-

Instead of melting snow on the runway surface by embedding pipes for hot water below said surface, the hot water may also be used to heat air that is subsequently blown in ducts 35 below the runway surface across the same. as shown in the modification illustrated in Figs. 6'8.

Snow melting by hot air can be done in such a way that ducts are built under the concrete surface. The best way is to make the top carpet of the runway reinforced or prestressed concrete, and obtain in this way a carpet free of joints and which can bridge all hollow spaces of the ground. The ducts 35 are about 2" to 6" deep and have a Width of 9" to 23 and serve to transfer heat at a high rate, provided the temperature of the air is kept at a high level, for instance at 200-300 F. It is best to arrange the ducts 35 under the concrete carpet in such a way so that the axis is neither parallel nor perpendicular to the axis of the runway. An acute angle of about to 45 is the most suitable for this purpose. In this way the snow sections which are molten on top of the channels carrying airof a higher temperature, will conduct the water across areas of lower melting capacity, and support in this way the melting of the snow in these areas, similar to the melting that has previously been described. The temperature drop of the hot air will depend on the thicknes of the concrete and on the amount of heat which has to be transferred to the surface.

Paired opposite heaters 36 and 31 are arranged on both sides of the runway and each pair of heaters cooperate to heat and blow the same mass of air in continuous opposite streams below the surface; one heater, for instance heater 36, blows the air into every second duct the same air is taken out on the other side of the runway from the heater 31 to be reheated and blown across the remaining ducts 35 and returned to the entrance of the rst heater 38. 'I'he heaters always substitute, or better, re-heat. the temperature loss of the air passing under the concrete. The same mass of air is always circulated by a pair of opposite heaters 36 and 31 so that a high efficiency is obtained. One pair of heaters 36 and 31 may serve about 20 to 30 ducts 35, which maybe located at center distances of 2 ft. The ducts 35 served by the heater 36 are placed at center distances of 4 ft.,

' and the ducts 35 served by the heater 31 (the second belonging to the pair), are disposed between these ducts, again at center distances of 4` ft., so that the actual center distances of the ducts are only 2 ft., and an excellent equalization of temperature is obtained.

/ The shape of the ducts and their insulation is of great importance. A layer 38 of insulating material is required at the bottom of the ducts, for instance consisting of'2" expanded concrete, or similar suitable insulating material. The side walls do not have to be insulated inasmuch as the bases of the side walls or pillars 33 between the ducts 35 are insulated by the layer 3B. The concrete cover or carpet 24 should be made as thin as possible in order to reduce the air temperature as far as possible and to make it feasible to work with larger air temperature drops. Even if the top layer consists of concrete of ,-6" thickness, an air temperature of 300F. is sufiicient to transfer a` heat output of 200 B. t. u. per sq. ft. to the runway surface I6. The cross-section of the ducts 35 is made in such a way-that the velocity is not reduced and so that in spite of the cooling of the air and notwithstanding the reduction in air volume, the same heat transfer throughout the whole length to the surface is obtained. This is done by shaping the rectangular duct crosssections, as best shown in Figs. 7 and 8: At the inlet 4| the duct 35 has a greater height but is of narrower width, and at the exhaust point 42 the height is reduced and the width considerably increased. The tops of the pillars 39 may preferably be covered with a flat steelI piece 43 in order to reduce the friction of the carpet 24 thereon.

As explained in the foregoing, opposite air streams are blown in both directions simultaneously to heat the runway surface. The heaters 36 and 31 are conventional type heaters and may be similar to the previously disclosed heaters 3|. The heat required to raise the temperature of the air stream to the desired level is taken from the hot water that is fed into the heaters 36 and 31 by the main pipes I2, and thencedischarged into the return pipes I3. A pair of opposite heaters 36 and 31 isarranged for every 20 or 30 ducts 35 and all the heaters along each side of the runway are fed by hot water generated in the power plant, as has been pointed out.

Although the foregoing surfaceheatlng exempliilcations are vdisclosed mainly in connection ,with runways, it will be understood that they are applicable for all airport surfaces including runways, taxi ways. loading and unloading aprons, etc. Furthermore, the pipelines may be so` arranged that thehot fluid is normally conducted to the airport buildings and hangars for space heating the 'same by convection from the pipes, and when snow conditions warrant it, is conducted into an additional pipe line from the buildings to the airport surfaces for heating the same, utilizing thereby the unused heat that remains in the fluid after passage through the buildings. Valves may be provided to permit connection and disconnection of the additional pipe line to the main pipe line.

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with specific' exemplifications thereof will suggest various other modifications and applications of the same. For instance, the particular arrangement of the coils embedded in the runway layer may be altered from the specific exemplification shown; likewise, the heaters 36 and 31 may be located at different points from these shown and the heaters may all be disposed along one side of the airport surface insteadf on both, and the airstream be returnedthereto after passing in opposite directions below ,the surface; also the ducts 35 may be disposed at a'different angle, without departing from the scope of the invention as pointed out in the claims hereof.

It is accordingly desired that in construing th breadth of the appended claims they shall not be limited to the specific exemplications of the invention described herein.

I claim:

1.` In a method of heating, a surface layer such as a pavement, the steps comprising, heating substantially incompressible fluid to an elevated temperature beyond the atmospheric boiling temperature thereof while at the same time subjecting it to pressure sufficient to maintain the liquid status thereof, storing the heated fluid at subsigned simultaneously to heat a surface from be low and to heat the region above the surface for dispersing fog therefrom, the steps comprising, heating liquid fluid to an elevated temperature beyond the atmospheric boiling temperature thereof while at the same time subjecting it to pressure suillcient to maintain the liquid status thereof, conducting a portion of said liquid into the surface to heat the same suillciently for melting snow or ice thereon, and utilizing the remaining liquid to heat a `stream o f air and subsequently to eject under force said airstream at predetermined spaced points above said surface and into the fog for dispersing the same.

3. In a method for use in connection with an airport, of combined surface heating and space heating and fog dispersal by means of heat, the steps comprising, heating substantially incompressible fiuidto an elevated temperature considerably above the atmospheric boiling temperature thereof while at the same time subjecting it to pressure sufficient to maintain the liquid status thereof, conducting said fluid in circuit, transferring heat from said fluid with relation to surfaces of said airport for heating the same, transferring heat from said fluid for space heating, transferring heat from said fluid to an airstream to be blown above said airport surface for dispersing fog thereon, and returning the fluid for reheating and subsequent re-use.

4. In a method oi.' fog dispersal for use in connection with an outdoor surface, the steps comprising conducting substantially incompressible fluid of highly elevated'temperatures in circuit, creating a forced airstream adjacent said circuit to receive heat from said fluid, and directing Said airstream in a plurality of spaced jet streams onto said surface, said jet streams having a predetermined temperature, sufllcient for dispersing fog.

5. In a method of combined building and surface layer heating, the steps comprising heating substantially incompressible fluid to an elevated temperature above the atmospheric boiling point thereof and subjecting it to pressure for restraining evaporation, conducting said fluid to a building for space-heating the same by convection, returning the fluid to the point of heating for re-heating and re-use, and selectively conducting at least a portion of said fluid from said building to a surface layer before returning the same to the heating point, for utilizing the unused heat remaining in said fluid from the passage through said buildings to heat the layer surface for snow or ice removal.

6. In a-system for heating a large area surface,

including means for heating and pressurizing incompressible fluids, in combination with, a carrier for said fluids interconnected to said means. a layer structure immediately below said surface and comprising an upper portion and a lower portion, said carrier including pipe lines embedded in said lower portion and spaced from each other substantially parallel to the said surface, and an insulator disposed above each pipe in alignment therewith and below said surface for depressing that portion of the heat flowing directly vertically upwardly from each pipe, to increase uniformly the temperature of said structure and thereby of said entire surface.

PAUL LUDWIG GEIRINGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Practice and Theory of Radiant Heating by Starbuck, 1949 edition pp. 97-101. 

